Magnetic series flasher having two electromagnetic coils and a magnetically reversible armature



Nov. 8, 1966 H. e. SIIBERG 3,234,735

MAGNETIC SERIES FLASHER HAVING TWO ELECTROMAGNETIC GOILS AND AMAGNETICALLY REVERSIBLE ARMATURE Filed July 12. 1965 \LAAA ATTORNEYSUnited States Patent MAGNETIC SERIES FLASHER HAVING TWO ELECTROMAGNETICCOILS AND A MAG- NETICALLY REVERSIBLE ARMATURE Hamming G. Siiberg,Union, N.J., assignor to Tung-Sol Electric Inc., a corporation ofDelaware Filed July 12, 1965, Ser. No. 471,120 Claims. (Cl. 33591) Thepresent invention relates to intermittently operating thermoresponsiveswitches and more particularly to a switch which can be employed forflashing automobile directional signal lamps. The new device isrelatively insensitive to changes in operating voltage, is of simpleconstruction, provides good contact life at high loads and has but asingle moving part.

The device employs as the moving element a metal having a low Curiepoint, such as the various nickel iron alloys which are magnetic at lowtemperatures and lose their magnetic properties when heated to or abovea predetermined higher temperature. By using the low Curie point metalfor the spring biased armature of a relay, the armature when cold willbe attracted by a magnetic field and when heated by current passingthrough the armature will lose its magnetic attractability and move toits retracted position under its spring bias. In prior thermomagneticrelays utilizing the Curie point effect, permanent magnets were employedwhich made the device very sensitive to change in voltage since thehigher the voltage the more rapid'heating of the armature with theresult of a decrease in the period of attraction and conversely at lowervoltages the period of attraction of the armature would increase.

In the device of the present invention two electromagnets are employedto act on a single armature so that the magnetic density of the coreswill compensate for any occurring voltage changes in the system.

The winding of one electromagnet provides the necessary force to pullthe armature into the circuit and also connects the power source inseries with the load, which for example, can be directional lamps to beflashed. The winding of this electromagnet has a high electricalresistance so as to prevent the lamps from lighting.

The winding of the second electromagnet is of low electrical resistanceand shunts the winding of the first electromagnet when the armature isattracted, thereby providing a low resistance path to the lamppermitting the lamps to light. The second electromagnet has sufiicientforce to hold the armature in attracted position so that the armaturewill heat up to its Curie point temperature and lose its magneticattractability. When the armature loses its magnetic permeability, thespring bias therein causes retraction of the armature to open thecircuit of the second electromagnet and thereby remove the shunt aboutthe winding of the first electromagnet.

In this arrangement, when the operating voltage increases, both thepull-in and hold-in forces increase, However, at the same time thecurrent through the armature, when the winding of the second magnet isenergized, increases and thereby raises the temperature of the armaturemore rapidly so that the Curie temperature is reached more quicklycausing the armature to be retracted sooner. Thus the increased voltageis compensated for in the system. In the same way, when the operatingvoltage decreases, the windings of the first and second electromagnetswill provide less attraction for the armature, but the armature whenheld will heat more slowly, thus lengthen ing the time before thearmature is released to compensate for the weaker forces applied by theelectromagnets.

Further, the present invention has the advantage of permitting differentdesign parameters for the two elec- 3,284,735 Patented Nov. 8, 1966vdesired speed and ratio when used as a flasher as will be explainedbelow.

For a better understanding of the invention and of the advantagesthereof, reference may be made to the accompanying drawing of which:

FIG. 1 is a flasher representing one embodiment of the invention andshown with the armature in the retracted position; and

FIG. 2 is the flasher of FIG. 1 shown with the armature in the attractedposition.

The flasher shown in the drawing includes a base 2 of insulatingmaterial such as a phenolic resin carrying two terminals 4 and 6 whichare molded therethrough. Terminal 4 above the base 2 supports aconductor 8 to which one of the ends of each of the windings 10 and 12is electrically connected. Winding 10, which is of low resistance havingrelatively few turns, encircles a U-shaped core 14. Winding 12 which isof relatively high resistance and has a relatively large number ofturns, encircles a larger U-shaped core 18. An armature 22 constructedof a metal having a relatively low Curie temperature, for example, anickel-iron alloy available under the trade name Nilvar or a nickelsteel alloy available under the trade name Invar, is fulcrumly mountedat its lower end on a bracket 24 supported from terminal 6. The armature22 has a spring bias therein tending to maintain the armature in theretracted position shown in FIG. 1. When the armature is attractedcontact 26 carried thereby engages a fixed contact 28 supported on apost 30. Post 30 is insulatedly mounted on the 'base 2.

The other end of winding 10 is electrically connected to contact 28 byway of post 30 and the other end of winding 12 is connected to core 18which is in conductive contact with bracket 24.

The operation of the above described device will be clear from thefollowing description. When one terminal of a source of energy isconnected to terminal 4 and a lamp load is connected between terminal 6and the other terminal of the source, current flows from terminal 4,post 8, winding 12, core 18, to bracket 24, terminal 6 and to the load.This current, because of the inclusion of the relatively high resistancewinding 12, will be insuflicient to light the lamps of the load.

The current in winding 12 develops a magnetic force in the U-shaped core18 which attracts armature 22 and brings the contact 26 carried therebyinto engagement with contact 28 as seen in FIG. 2. Current thereuponflows from terminal 4 and post 8 through winding 10, post 30, contacts28 and 26, armature 22, terminal 6 and the load. The winding 10 providesa low resistance shunt for winding 12. The current through winding 10and the armature 22 is suflicient to heat the armature and thereby raiseits temperature to the Curie point. This current is also sufficient tocause illumination of the lamps of the load.

When the magnet properties of the armature 22 are reduced at the raisedtemperature to a point where the spring bias in the armature overcomesthe magnetic pull on the armature from U-shaped core 14, the armaturesnaps back into the position shown in FIG. 1, opening the circuit andopening the shunt about the winding 12. Accordingly, the coil 12 isagain energized developing a magnetic force in the U-shaped core 18which in turn attracts the armature when it has cooled sufficiently toregain its magnetic properties. In this manner the cycle will repeatitself.

Thus, in the new device, the magnetic forces are supported by twoseparate magnetic circuits working alter- "nately. The invention has theadvantage, as heretofore explained, of permitting different designparameters for I hold-in force and pull-in force and of providingautotact, by varying the spring force in the armature necessary to openthe shunt circuit or by variation in the relative number of turns of thewindings.

It will be clear from the foregoing description that the inventionprovides a single rugged voltage compensated flasher or the like whichrequires a single moving part and which lends itself to readyadjustment. Obviously, various changes in the illustrated constructioncould be made without departing from the spirit of the invention or thescope of the accompanying claims as will be apparent to those skilled inthe art.

The following is claimed:

1. An intermittently operating thermoresponsive switch comprising:

(i) an armature fulcrumed at one end thereof and composed of materialwhich loses its magnetic permeability upon heating,

(ii) a first electromagnet having a high electrical resistance windingand a second electromagnet having a low electrical resistance winding,

(iii) means connecting said first electromagnet so that when energizedit attracts said armature to said second electromagnet to be heldthereby in the attracted position in which position the Winding of thefirst electromagnet is shunted until said armature moves from saidattracted position because of loss of its magnetic permeability.

2. An intermittently operating thermoresponsive switch comprising:

(i) an armature fulcrumed at one end thereof and having a first contactat the other end thereof, said armature composed of material which losesits magnetic permeability upon heating by current passing therethrough,

(ii) a first electromagnet having a high electrical resistance windingand a second electromagnet having a low electrical resistance winding,

(iii) the winding of said second electromagnet having one of its endsterminating at a second contact,

(iv) and said armature when magnetically attracted by said firstelectromagnet, carries said first contact into engagement with saidsecond contact to shunt the coil of said first electromagnet and to heatsaid armature.

3. An automobile flasher switch comprising:

(i) a base of electrically insulating material having at least twoterminals passing therethrough,

(ii) an armature fixed in contact with a first one of said terminals andhaving a first contact at its free end, said armature composed ofmaterial which loses its magnetic permeability upon heating by currentpassing therethrough,

(iii) a first electromagnet having a high electrical resistance coil anda second electromagnet having a low electrical resistance coil.

(iv) the coil of said first electromagnet having its ends connectedacross said terminals,

(v) the coil of said second electromagnet having one of its endsconnected to the second one of said terminals and its other endconnected to a fixed second contact, 7

(vi) said armature when magnetically attracted by said firstelectromagnet carries said first contact into engagement with saidsecond contact to shunt the coil of said first electromagnet by the coilof the second electromagnet and to heat the armature.

4. The flasher of claim 3 wherein said armature is spring biased toretracted position in which said contacts are separated.

5. The flasher of claim 3 wherein the magnetic force from said firstelectromagnet is sufiicient to pull the armature towards it and saidsecond electromagnet has a sufficient magnetic force to hold thearmature after the coil of said first electromagnet is shunted andbefore the armature loses its magnetic permeability.

No references cited.

BERNARD A. GILHEANY, Primary Examiner. R. N. ENVALL, JR., AssistantExaminer.

1. AN INTERMITTENTLY OPERATING THERMORESPONSIVE SWITCH COMPRISING: (I) AN ARMATURE FULCRUMED AT ONE END THEREOF AND COMPOSED OF MATERIAL WHICH LOSES ITS MAGNETIC PERMEABILITY UPON HEATING, (II) A FIRST ELECTROMAGNET HAVING A HIGH ELECTRICAL RESISTANCE WINDING AND A SECOND ELECTROMAGNET HAVING A LOW ELECTRICAL RESISTANCE WINDING, (III) MEANS CONNECTING SAID FIRST ELECTROMAGNET SO THAT WHEN ENERGIZED IT ATTRACTS SAID ARMATURE TO SAID SECOND ELECTROMAGNET TO BE HELD THEREBY IN THE ATTRACTED POSITION IN WHICH POSITION THE WINDING OF THE FIRST ELECTROMAGNET IS SHUNTED UNTIL SAID ARMATURE MOVES FROM SAID ATTRACTED POSITION BECAUSE OF LOSS OF ITS MAGNETIC PERMEABILITY. 